Many mechanisms have been devised for installation on cabinet doors and the like to provide positive locking of the doors in closed position while permitting convenience in operation of the door. An important feature often sought to be attained is to make it harder to open the door than to close it to discourage unauthorized access. Other objectives are simplicity in operation, manufacture and construction, as well as installation. The closest art to the invention of the applicant is set forth below.
Bacon, U.S. Pat. No. 2,552,390 employs a cam faced latch employing a coiled spring which works through a link and lever machanism so that the action of the spring is to hold the latch against the catch when opening the door and aid the operation of the latch when closing the door.
Nottingham, U.S. Pat. No. 2,626,170 likewise uses a spring, in this case a leaf spring, operating against a pin in a slot in the cam so that because of the configuration of the latch member, the combined action of the spring and pin against it also requires more force to open and to close.
Sealey, U.S. Pat. No. 4,230,352 uses a complicated combination of rollers, latches and cam, the rollers being spring-loaded so that pressure externally on the door is transmitted through the linkage to release the catch and permit the door to open.
While applicant also employs a spring, cam, and rollers or pins, he uses them in an entirely different combination and configuration so that the method of operation of his latch differs entirely from that of the prior art as will be evident from the description below.